The shortage of head teachers is likely to reach crisis point up to five years earlier than predicted.

Jon Sheridan, local education authority development manager at Select Education, told Recruiter that based on research by the National College of School Leadership "the shortage of head teachers will reach a critical stage between 2009 and 2011".

Previous research by the Times Educational Supplement predicted that half of all school leaders would retire by 2014, but according to the new research, the number of head teachers leaving the profession will now spike between 2009 and 2011. Further recent research by Education Data Research confirms that the crisis has hit the sector sooner than previously expected, said Sheridan. It found that 35% of all head teaching jobs are re-advertised, a figure that rises to 55% in London.

This compares with around 20% of advertised posts that went unfilled in 2005, according to a report commissioned by the Secondary Heads Association and the National Association of Head Teachers in July 2005.

As well as the large number of teachers approaching retirement age, the worsening situation has been caused by a shortage of teachers with the necessary experience, according to Sheridan.

"The next three years will be a time of significant change and challenge in the education sector," predicts Sheridan.